1. Field of the Invention
The first present invention relates to a toner which is suitable for use in copiers, printers, plotters, faxes and the like. More particularly it relates to a toner in which silicone fine particles are used as an external additive, allowing image fogging to be controlled and higher image density to be maintained so as to improve contrast.
The second present invention relates to a dry-development toner that contains, as its principal component, resin particles having been colored with a dye, and that is suitable for use in copiers, printers, plotters, faxes and the like. More particularly it relates to a dry-development toner in which fogging, blank spots, and other image defects caused by the presence of charge-controlling agents can be prevented, and in which the strength with which images are fixed to printing paper can be improved, by coating the surfaces of resin particles with a fine organic powder by means of mechanical impact force without the use of charge-controlling agents.
2. Related Art of the Invention
With respect to the related art of the first present invention, various types of toners have been proposed in the past for toners used in copiers and the like. In such toners, to the toner particles (virgin toner particles) such as polymer resin particles or powdered resin particles, are externally added some type of an organic fine powder or inorganic fine powder to improve the fluidity or the like. Of these fine powders, the hydrophobic silica fine particles are most generally used.
The external addition of the hydrophobic silica fine particles to virgin toner particles is made by mixing the hydrophobic silica fine particles with the virgin toner particles, and further stirring the mixture for a predetermined period of time in a mixer. This allows the hydrophobic silica fine particles to be completely and uniformly added to the whole of the virgin toner particles. The toner in which the hydrophobic silica fine particles are externally is then sifted as needed to remove coarse powder such as foreign matters, and it is then ultimately made into a final toner product.
The toner which has been prepared in the manner described above has better fluidity due to the presence of the hydrophobic silica fine particles, and may be used in a variety of image-forming devices.
Image-forming devices such as copiers and printers, however, involve the use of various image-forming processes, and the properties of the toner needed for each type of image-forming process generally differ somewhat. In such cases, the toner particles themselves are sometimes improved or modified in order to ensure that the toner properties are suited to the image-forming process. However, such improvement or modification of the toner particles themselves often produces new inconveniences. Accordingly, an external additive to be mixed with the toner particles is commonly changed to another one.
In view of the foregoing, it is difficult to make toner suitable for the various image-forming processes used in image-forming devices simply by externally adding silica fine particles as the external additive to the toner particles as in the aforementioned conventional toner. Some problems that still persist are the inability to obtain adequate contrast because of the low solid density of the images, image fogging, and a low toner projection rate onto the printing paper.
With respect to the related art of the second present invention, various toners have been proposed in the past as dry-development toners. In image-forming processes using such toners, it is natural that these toners be required to have positive or negative electrification properties. In such cases, charge-controlling agents are commonly added to toners in order to endow it with either type of electrification properties and to control the static charge thereof. Nigrosine-based nucleophilic dyes and the like are used in such cases as charge-controlling agents to impart positive electrification properties to toners, and electrophilic organic complexes composed of oil-soluble metallized dyes and the like are used as charge-controlling agents to impart negative electrification properties to toners.
Although toner electrification can be controlled when such charge-controlling agents are added to toners, these charge-controlling agents are also known to greatly affect toner characteristics other than electrification control.
The addition of charge-controlling agents brings about, for examples, problems in which the photosensitive drums in image-forming devices are contaminated with toners during image formation, raising the residual potential of the photosensitive media on the photosensitive drum and causing image fogging, and in which, conversely, the residual potential of the photosensitive media is lowered, causing blank spots in the images. Another problem is that charge-controlling agents used in a two-component developing toner contaminate the carrier and reduce the static charge of the toner, making it impossible to form images in an appropriate manner.